Birds robustly regenerate their cochlear hair cells through the conversion of dormant supporting cells into new hair cells. Our project uses selective, high-sensitivity methods to reveal the molecular changes in supporting cells after their activation by, for example, ototoxic drugs that cause hair cell death. By examining the responses of many single cells, we have begun to identify triggers that initiate, execute, sustain, and ultimately terminate the regenerative process. Recent experiments have confirmed what we already knew, that the two halves of the chicken cochlea (neural and abneural) predominantly use different regeneration mechanisms. Using bioinformatics methods to process the resulting data, this year we are focusing on analyzing chicken cochlea cell populations isolated at various time points during hair cell regeneration and specifically characterizing the two distinct responses. By examining regeneration in an animal that replaces hair cells after damage, we will be able to find triggers that may be activated in mammals to reverse hair cell loss.